The present invention relates to a backlight generating apparatus of a liquid crystal display (LCD) device, and, more particularly to a backlight generating apparatus of an LCD device with an improved light-diffusing structure for increasing light efficiency.
Generally, an LCD device, as shown in FIG. 1, comprises polarizing filter layers 1 on both of its outer surfaces. Front and rear plates 2 and 3 form a closed space filled with liquid crystal 6 by means of sealing material 7 placed on the inside edges of the LCD device. A number of transparent electrodes 4 are disposed on the front plate 2 and the rear plate 3 in an opposing relationship. An orientation layer 5 coats the upper part of transparent electrodes 4 and the whole inner surface of the front plate 2 and the rear plate 3 which is exposed between the transparent electrodes.
The above LCD device is not a self-luminous device such as a cathode-ray tube or a vacuum fluorescent display, but a non-emissive display which performs the display by means of light from outside.
There are two kinds of LCD devices--a front reflection-type LCD which shows the predetermined pattern generated by the alignment of crystal liquid 6 using the light incident through front plate 2 and a transmission-type LCD which uses the backlight of a backlight generating apparatus incident from the rear side of the LCD to realize the display. The present invention relates to the latter, the backlight generating apparatus of a transmission-type LCD.
The conventional structure of the backlight generating apparatus of the transmission-type LCD is illustrated in FIG. 2. The illustrated backlight generating apparatus comprises a diffusing plate 11 placed facing the bottom of the rear plate 3 of an LCD device and separated from the rear plate 3 by a polarizing filter layer 1. A light-passing plate 12 is installed to the bottom of a diffusing plate 11, and a reflecting plate 13 is installed to the bottom of a light-passing plate 12 for reflecting the diffused light entering the light-passing plate 12 toward diffusing plate 11. For providing light to the light-passing plate 12, a lamp L is placed on one side of light-passing plate 12. Lamp L has a fluorescent film and reflecting film having a combined predetermined thickness, and is installed in a housing H.
In a conventional backlight generating apparatus constructed as above, the light irradiated from lamp L is irradiated onto the diffusing plate 11 via the light-passing plate 12, and then diffused by the diffusing plate 11 and directed to the rear plate of an LCD.
However, in such a conventional backlight generating apparatus, since the incident light is diffused only by diffusing plate 11, a considerable amount of the light generated from lamp L is lost. Therefore, due to the small amount of light-passing through the diffusing plate 11 onto the rear plate, a picture having sufficient brightness cannot be viewed through the LCD. This is because it is impossible to use a diffusing plate having a suitable transmissivity for diminishing the partial brightness difference of a picture. Since the transmissivity of a conventional diffusing plate is about 20-30%, a considerable amount of light is lost in the diffusing plate, thus decreasing the amount of light contributing to the display of the picture. Accordingly, heretofore, power has been applied to the lamp to compensate for the diminished brightness. However, this necessitates an undesirable increase in total power consumption.